Relevance ~ EXTERNAL VALIDITYsample sizerandomisationcontrolling for differencestoo short a follow up periodvariation in the interventionpoorly defined or described study populations.Improving the quality of studiesbar set low - misleading estimatesstudy 1study 10study 8study 7study 6study 5study 4study 3study 2study 9High Qualitystudy 1study 10study 8study 7study 6study 5study 4study 3study 2study 9Low Qualitystudy 1study 10study 8study 7study 6study 5study 4study 3study 2study 9How the actual study deviates from the idealised version of it will reveal all internal and external biases, which are dealt with separatelyThe next steps are to find an appropriate statistical model for including both internal and external bias adjustment, and then to quantify bias.Tools for identifying internal biases and external biases separately and by different members of the research team with different skills are provided by Turner et al.The end result of these steps is an bias adjusted meta-analysis that emerges from methods that can be implemented routinelyDistributions are required for each bias in each study, which could be gained from eliciting expert opinion by extracting qualitative details of study characteristics that might be a source of bias for each bias category and then revealing ranges of the bias on elicitation scalesIndeed the authors suggest that for each study the bias elicitation process lasted one hour plus a minimum of one hours preparation and then the completion of the bias check list required at least three hours.identify all potential internal and external biases by imagining an idealised version of each study under consideration and writing a mini-protocol for itneither one or the otherbar set high - large uncertaintystudy 1study 10study 8study 7study 6study 5study 4study 3study 2study 9The ideal situationWhich data to use?“this review has not been been able to provide evidence of the effect of interventions to promote hand hygiene”“the findings should not be taken to suggest that attempts to increase compliance or reduce HCAI are not worth undertaking”“logically hand hygiene seems an important and cost-effective intervention.......and should continue to be promoted in all clinical settings”JudgementsDecisionsAny Questions?